In an open letter to the country's prime minister, Hun Sen, and the health minister, Mam Bunheng, more than 100 international and domestic pressure groups said they were deeply disturbed by the "life-threatening" conditions in the settlement.

Forty families are forced to live in sheet-metal sheds without running water or proper sanitation.

The government has spent the past two months moving people with HIV/Aids from the Borei Keila district of Phnom Penh to Tuol Sambo, a flood-prone area 15 miles (25km) away.

"By bundling people living with HIV together in second-rate housing, far from medical facilities, support services and jobs, the government has created a de facto Aids colony," Shiba Phurailatpam, of the Asia-Pacific Network of People Living with HIV/Aids, said.

Rebecca Schleifer, a Human Rights Watch spokeswoman, said conditions at Tuol Sambo posed "serious risks" to people who were already vulnerable to illness.

"People living with HIV have compromised immune systems and are especially vulnerable," she added. "For them, these substandard conditions can mean a death sentence or a ticket to a hospital."

According to Médecins sans Frontières, conditions at Tuol Sambo do not meet the minimum international standards for temporary housing.

The families were evicted from Borei Keila to make way for a commercial development, which was reportedly granted government approval on the understanding that the developer would place the residents, including those with HIV/Aids, into new housing.

The evictions continued despite protests from UN agencies, and the campaigners' letter said: "We have reason to fear that relocations of HIV-affected families are continuing even as we sign this letter."

They urged the government to stop moving families to Tuol Sambo, urgently improve living conditions there and ensure that people with HIV have access to antiretroviral drugs.

Local officials said they were aware of the concerns over the settlement and were trying to improve conditions.

"We are trying to find clean water for them," Phnom Penh's deputy governor, Mann Chhoeun, told the Phnom Penh Post, adding that plans had been made to distribute free medicine via the Centre of Hope mission.

In 2008, according to UNAids, an estimated 67,200 adults and 3,800 children in Cambodia were living with HIV/Aids.